Living Landscapes in South Dakota - Plant Materials Program - US ...

Landscape for Cooling Efficiency
Trees and shrubs can provide valuable shade to a house, reducing energy consumed
for air conditioning. A shaded roof reduces house temperature as much as 10 degrees.
Tall, deciduous trees are preferred for roof shade. Their structure provides shade in
summer but lets sunlight through in winter. Optimum distance from tall shade trees to
a building is 15 to 20 feet. Sturdy species such as bur oak, hackberry, or green ash
are preferred to reduce the risk of broken limbs damaging the building. Proper pruning
as the trees grow is crucial for strong limbs and trunks, and prevents rubbing damage
to the siding or roof. Instructions are found in the NDSU Extension Service Bulletin
“Pruning Trees and Shrubs” at
http://www.ext.nodak.edu/extpubs/plantsci/trees/h1036w.htm.
Tall trees planted on the east side and southeast corner intercept the morning sun,
significantly slowing the warm-up process in the summer. Tall trees on the south side
block valuable sunlight in winter. Tall trees on the west side and southwest corner
provide valuable shade from the summer sun on hot afternoons and evenings.
Shrubs planted close to the house on the west and east sides can intercept or defl ect
solar heat, reducing interior temperature. Choose species that are adapted for the
space and size of the wall to be screened. Where rubbing damage could occur, plant
shrubs far enough away from the house or prune them as needed.
Vines can also be grown near or on buildings to intercept solar heat. Selecting a
species with desired traits is important. Not all vine species are capable of climbing
bare walls. Riverbank grape is a native vine that will produce edible fruit if pruned
annually. It is not adapted to climb a bare wall but is suited to a trellis. Woodbine is
another native vine that is well suited to intercept solar heat. If you fi nd vines visually
appealing, they may have a niche in your landscape. Information about different vine
species is available from the NDSU Extension Service,
http://www.ext.nodak.edu/county/cass/horticulture/treeshrub/vines.htm.
Air conditioners and heat pumps will consume less energy if they are shaded. A
tall shrub or vine-covered arbor can provide shade and attractively screen such
equipment. Leave at least 5 feet of clear space around air conditioners and heat pumps
for air circulation and maintenance. Place the plant so that at maturity it will shade the
air conditioner or heat pump when the appliance is running.
Landscape to Minimize Maintenance
Lawn mowing burns 800 million gallons of gasoline annually in the USA. About 90
million pounds of pesticides are put on lawns and gardens annually. Irrigating a 75 x 100
square-foot lawn with ¾ inch of water twice a week for eight weeks demands pumping
and paying for 56,000 gallons of water. Substantial amounts of chemicals and energy
are used to treat and pump municipal and rural water applied to lawns. Landscaping with
native plants minimizes mowing, watering, fertilizing, and pesticide inputs.
Most lawns in South Dakota are Kentucky bluegrass. They are mowed frequently from
May through September. They are regularly irrigated in western South Dakota, and
commonly irrigated elsewhere in the state. Fertilizer and herbicides are often applied to
this introduced species.
Blue grama and buffalograss are short, native perennial grasses, that are alternatives
to Kentucky bluegrass for lawns. They are drought-tolerant, warm-season species
that grow very little before June or after August. These short species require only 3
to 4 mowings per year and no fertilizer. Irrigation may be required for establishment.
Established stands do not require irrigation and spring or fall watering may encourage
weed growth. During drought and periods of dormancy, these species turn a tan color.
Photo courtesy of SDSU Cooperative Extension Service
Buffalograss lawns require far less energy, time, and money to maintain than Kentucky bluegrass.
Buffalograss prefers clay to loamy soil, while blue grama is adapted to soils ranging from
sand to clay. They look alike and can be grown alone or together. Planted as a mixture,
blue grama and buffalograss have a uniform appearance.
One plan would be to plant Kentucky bluegrass next to the house and native species on
the remainder. A strip of native flowers can attractively separate the Kentucky bluegrass
from the low-maintenance blue grama/buffalograss area.
Irrigation costs can be reduced by piping or channeling roof runoff toward trees, a rain
garden, or native flowerbeds. The runoff from some driveways can likewise be diverted to
enhance plant growth and vigor.
Mulch can be used for saving water, labor, and energy. Wood chips, leaves, grass
clippings, or other organic matter around trees, shrubs, and flowers lower soil
temperature and reduce evaporation. A layer of mulch 2 to 3 inches thick will usually
control weeds. Mulch materials can often be obtained free from a city maintenance
department, neighbors, or utility company. More information about mulching is available
at http://www.nrcs.usda.gov/feature/backyard/Mulching.html.
Snow is an important consideration in landscaping. Windbreaks, yard trees, and shrubs
will reduce snowblower work and fuel consumption if correctly placed. Spruce and
juniper trees with low-level branches intact provide maximum density and trap snow in
the shortest, deepest drifts. Deciduous trees with the lower branches removed yield the
longest drifts. Multiple tree rows increase density and shorten snow drifts.
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Energy Conservation